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In the Northern and Southern hemispheres, influenza infections occur seasonally. So far, Influenza outbreaks are observed every winter in Switzerland. From one year to the next the influenza outbreak varies in intensity, duration, circulating viral strains and the impact on the population. In order to inform the population and doctors of time of the wave of influenza and the coverage of influenza by the vaccine, the FOPH publishes from October to April a weekly report with a risk assessment.
The spread of influenza illness in Switzerland is currently widely spread. During week 3, 142 physicians from the Sentinella surveillance system reported 17.3 cases of influenza 1000 consultations. Extrapolated to the general population, this rate corresponds to an incidence of 140 consultations due to influenza illness per 100,000 population. The seasonal epidemic threshold of 68 cases of influenza illness per 100,000 population was exceeded in week 2/2019 (Figure 1).
The highest incidence was in the 0-4 old age group (Table 1). The spread of influenza is widespread in the Regions 1 (GE, NE, VD, VS) and 4 (LU, NW, OW, SZ, UR, ZG), and very widespread in the Regions 2 (BE, FR, JU), 3 (AG, BL, BS, SO), 5 (AI, AR, GL, SG, SH, TG,ZH) and 6 (GR, TI).
Figure 1: Number of weekly visits due to influenza illness, extrapolated per 100,000 population
Figure 2: Incidence of consultations per 100,000 population and spread by Sentinella region during week 3/2019
During week 3, the National Influenza Reference Center (NCRI) detected Influenza A viruses in 25 of the 53 samples analyzed as part of the Sentinella surveillance system. Since the beginning of the influenza season, the CNRI has demonstrated by inhibition of haemagglutination the following viruses in Sentinella samples:
- A/St Petersburg/27/2011-like
- A/Hong Kong/4801/2014-like
1. European Centre for Disease Prevention and Control (ECDC). Seasonal Influenza - Latest surveillance data http://flunewseurope.org/ (accessed on 08.01.2019).
2. Weekly U.S. Influenza Surveillance Report http://www.cdc.gov/flu/weekly/index.htm (accessed on 08.01.2019).
3. Canada Rapports hebdomadaires d’influenza. http://www.canadiensensante.gc.ca/diseases-conditions-maladiesaffections/disease-maladie/flu-grippe/surveillance/fluwatch-reports-rapports-surveillance-influenza-fra.php (accessed on 20.11.2018).
4. China National Influenza Center weekly reports. http://www.chinaivdc.cn/cnic/ (accessed on 08.01.2019).
5. World Health Organisation (WHO) Influenza update – 332 http://www.who.int/influenza/surveillance_monitoring/updates/latest_update_GIP_surveillance/en/ (accessed on 08.01.2019).